This document discusses, among other things, apparatus and methods for transmit beamforming sounding. An example method for communicating over a wireless network having multiple sub-carrier frequencies can include assigning a first pilot signal to a first sub-carrier frequency for transmission with a first symbol, transmitting the first symbol from a first wireless device, receiving the first symbol at a second wireless device, determining channel time and phase offset using the first pilot signal, and estimating transmit beamforming channel state information using the first pilot signal.
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1. A method performed by an apparatus of a wireless device, the method for communicating over a wireless network having multiple sub-carrier frequencies, the method comprising: receiving a plurality of symbols, each symbol comprising a plurality of sub-carriers and one or more pilot signals positioned at a sub-carrier frequency wherein for the plurality of symbols a pilot signal of the one or more pilot signals is positioned in a different one of each of the plurality of sub-carriers for at least one symbol of the plurality of symbols; determining channel time and phase offset using the one or more pilot signals; and estimating transmit beamforming channel state information using the one or more pilot signals.
A wireless device receives a series of communication symbols across multiple sub-carrier frequencies. Each symbol includes pilot signals located at specific sub-carrier frequencies. Crucially, the pilot signal's position varies across different symbols, ensuring that over the entire series, a pilot signal occupies a different sub-carrier in at least one of the symbols. The device then uses these pilot signals to determine channel time and phase offsets and subsequently estimates transmit beamforming channel state information. This information helps optimize wireless communication.
2. The method of claim 1 , including transmitting the transmit beamforming channel state information to the first wireless device.
In addition to the process described previously, the wireless device, after determining channel characteristics using traveling pilot signals, transmits the resulting transmit beamforming channel state information back to the originating wireless device. This feedback allows the transmitting device to adapt its beamforming for improved communication. This process is done to enhance communication and optimize beamforming.
3. The method of claim 1 , wherein determining channel time and phase offsets using the one or more pilot signals includes removing an overlay from the one or more pilot signals, the overlay configured to assist to resolve channel dimensions when the first wireless device includes more than one transmit antenna.
When determining channel time and phase offsets using traveling pilot signals, the wireless device removes a special "overlay" from the pilot signals. This overlay is specifically designed to aid in resolving channel dimensions, particularly when the transmitting wireless device uses multiple transmit antennas. Removing this overlay allows for a more accurate determination of channel characteristics in multi-antenna systems.
4. The method of claim 1 , wherein estimating the transmit beamforming channel state information includes averaging the transmit beamforming channel state information over a packet length.
The wireless device estimates transmit beamforming channel state information by averaging the channel state information derived from the traveling pilot signals over the length of a data packet. This averaging process smooths out short-term fluctuations and provides a more stable and reliable estimate of the channel conditions.
5. The method of claim 1 , wherein estimating the transmit beamforming channel state information includes time-weight averaging the transmit beamforming channel state information over a packet length to better estimate a Doppler effect.
To better account for the Doppler effect, the wireless device estimates transmit beamforming channel state information by using time-weighted averaging of the channel state information derived from traveling pilot signals over the length of a data packet. This gives more weight to recent channel estimates, allowing the system to adapt more quickly to changing channel conditions caused by movement.
6. A method performed by an apparatus of a first wireless device, the method for communicating over a wireless network having multiple sub-carrier frequencies, the method comprising: assigning one or more pilot signals to each of a plurality of sub-carrier frequencies of each of a plurality of symbols according to a predetermined pattern to assist with determining transmit beamforming channel state information, wherein the predetermined pattern indicates that for the plurality of symbols a pilot signal is to be assigned to a different one of each of the plurality of sub-carriers for at least one symbol of the plurality of symbols configuring the first wireless device to transmit the plurality of symbols; and receiving transmit beamforming channel state information derived from the plurality of symbols from a second wireless device.
A wireless device assigns pilot signals to different sub-carrier frequencies within a series of transmitted symbols, following a predetermined pattern. This pattern ensures that, across the series, a pilot signal occupies a different one of each of the sub-carriers for at least one symbol. This arrangement is designed to assist in determining transmit beamforming channel state information. The device then transmits these symbols and receives transmit beamforming channel state information derived from these symbols from a second wireless device.
7. The method of claim 6 , including applying an overlay to each of the one or more pilot signals, the overlay configured to assist resolve channel dimensions when the first wireless device includes more than one transmit antenna.
The transmitting wireless device applies a special "overlay" to each of the traveling pilot signals. This overlay is designed to help the receiving device resolve channel dimensions, which is particularly important when the transmitting device uses multiple transmit antennas. The overlay effectively adds information to the pilot signals that aids in separating and identifying the different channels.
8. The method of claim 6 , wherein the overlay is associated with a column or row of an overlay matrix.
The "overlay" applied to each pilot signal corresponds to a specific column or row from a larger "overlay matrix." This matrix provides a structured way to encode information into the pilot signals, allowing the receiving device to differentiate between multiple transmit antennas or spatial streams.
9. An apparatus of a first wireless device, the apparatus comprising: memory; and processing circuitry coupled to the memory, the processing circuitry configured to: position each of one or more pilot signals within one of a plurality of sub-carriers of each of a plurality of symbols according to a predetermined pattern to assist with determining transmit beamforming channel state information, wherein the predetermined pattern indicates that for the plurality of symbols a pilot signal is to be positioned in a different one of each of the plurality of sub-carriers for at least one symbol of the plurality of symbols; configure the first wireless device to transmit the plurality of symbols; receive transmit beamforming channel status information based on the one or more pilot signals from a second wireless device; and adjust transmit parameters based on the transmit beamforming channel status information.
A wireless device includes memory and processing circuitry. The circuitry positions traveling pilot signals within sub-carriers of symbols according to a predetermined pattern. The pattern ensures that the pilot signal is positioned in a different one of each of the sub-carriers for at least one symbol. It then transmits these symbols, receives beamforming channel status information based on these pilot signals from another device, and adjusts its transmit parameters based on this received channel information.
10. The apparatus of claim 9 , wherein the predetermined pattern includes assigning the pilot signal at a first sub-carrier frequency for a number of sequential symbols before placing the pilot signal at a second sub-carrier frequency.
The predetermined pattern for positioning the traveling pilot signals involves assigning the pilot signal to a specific sub-carrier frequency for several consecutive symbols before shifting the pilot signal to a different sub-carrier frequency. This creates a pattern of pilot signals that "travels" across the sub-carriers over time.
11. The apparatus of claim 10 , wherein the number of sequential symbols is equal to the number of antennas associated with the wireless transmitter.
The number of sequential symbols for which a pilot signal remains at a given sub-carrier frequency is equal to the number of antennas associated with the wireless transmitter. This synchronization between pilot signal duration and the number of antennas helps the receiver distinguish signals from each antenna.
12. The apparatus of claim 9 , wherein the processing circuitry is further configured to apply an overlay to each pilot signal of the one or more pilot signals, wherein the overlay corresponds to a predetermined matrix used with a wireless receiver.
The processing circuitry also applies an "overlay" to each traveling pilot signal. This overlay corresponds to a predetermined matrix used by the receiving wireless device. This matrix provides information that helps the receiver separate signals from multiple transmit antennas or spatial streams.
13. The apparatus of claim 9 , wherein the processing circuitry is further configured to: encode data into each of the plurality of symbols.
In addition to managing pilot signal placement and overlays, the processing circuitry also encodes data into each of the transmitted symbols. This ensures that the symbols carry both the pilot signals used for channel estimation and the actual data being transmitted.
14. An apparatus of a wireless device, the apparatus comprising: memory; and, processing circuitry coupled to the memory, the processing circuitry configured to: receive a plurality of symbols, each symbol comprising a plurality of sub-carriers and one or more pilot signals positioned at a sub-carrier frequency wherein for the plurality of symbols a pilot signal of the one or more pilot signals is positioned in a different one of each of the plurality of sub-carriers for at least one symbol of the plurality of symbols; and estimate transmit beamforming channel state information using the one or more pilot signals.
A wireless device receives a series of communication symbols. Each symbol contains multiple sub-carriers and one or more pilot signals positioned at some of these sub-carriers. The key is that for these series of symbols, the pilot signal is positioned in a different one of each of the sub-carriers for at least one symbol. The device then estimates transmit beamforming channel state information by analyzing the pilot signals.
15. The apparatus of claim 14 , wherein the processing circuitry is configured to average the beamforming channel state information over a packet of symbols, wherein the packet includes at least a portion of the plurality of symbols.
The processing circuitry averages the beamforming channel state information over a packet of symbols. This packet includes at least a portion of the series of symbols received. This averaging smooths out fluctuations in the channel and provides a more stable estimate for beamforming.
16. The apparatus of claim 15 , wherein the processing circuitry is configured to time-weight average the beamforming channel state information over the packet of symbols.
The processing circuitry uses time-weighted averaging of the beamforming channel state information over a packet of symbols. This means that more recent channel state estimates are given greater weight in the averaging process, allowing the device to adapt more quickly to changes in the wireless channel.
17. The apparatus of claim 14 , wherein the processing circuitry is configured to remove an overlay from each pilot signal to provide an un-layered pilot signal and to determine channel time and phase offsets using the un-layered pilot signal, wherein the overlay corresponds to an element of a predetermined matrix used with a transmitter of the plurality of symbols.
The processing circuitry removes an "overlay" from each traveling pilot signal to obtain a "un-layered" pilot signal. It then uses the "un-layered" pilot signal to determine channel time and phase offsets. The removed overlay corresponds to an element of a predetermined matrix used by the transmitter of the symbols.
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October 11, 2013
June 6, 2017
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